The present invention relates to a threading apparatus.
Threading apparatuses are widely known. In a known threading apparatus the switchable, form-locking coupling device is formed as a claw coupling. This construction as well as other structural elements have the disadvantage that the coupling device is subjected to high wear. This is especially true for threading apparatuses with or without rotary direction reverse transmission for threading with high rotary speeds and without rotary direction change of the driving machine spindle driven with high rotary speed, for example in the range of 2,500 revolutions per minute. All torque-transmitting structural elements must satisfy high requirements. During cutting of a right-handed thread, for example, the coupling devices switch so that the first coupling part is connected with a switching member and thereby with the driving part coupled with the switching member in a torque-transmitting connection. In contrast, the second coupling part is not coupled with the switching member. A rotary direction change to left-handed, for example, for turning out of the tap is performed by the axial displacement of the switching member and uncoupling of the first coupling part and coupling of the second coupling part. In this case there is high rotary speed difference, and therefore a high acceleration is produced. As a result there is a problem to provide a wear-free coupling of the switching member with the second coupling part and also to transmit the high rotary speed differences and thereby require accelerations so as to maintain the wear of the individual part as low as possible. The first goal is achieved in the threading apparatus in that during drilling of threaded openings a maximum accurate thread depth is achievable and it is worked at the above mentioned high rotary speeds.